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scv_shared_ptr.h

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//  -*- C++ -*- <this line is for emacs to recognize it as C++ code>
/*****************************************************************************

  The following code is derived, directly or indirectly, from the SystemC
  source code Copyright (c) 1996-2002 by all Contributors.
  All Rights reserved.

  The contents of this file are subject to the restrictions and limitations
  set forth in the SystemC Open Source License Version 2.3 (the "License");
  You may not use this file except in compliance with such restrictions and
  limitations. You may obtain instructions on how to receive a copy of the
  License at http://www.systemc.org/. Software distributed by Contributors
  under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF
  ANY KIND, either express or implied. See the License for the specific
  language governing rights and limitations under the License.

 *****************************************************************************/

/*****************************************************************************

  scv_shared_ptr.h -- 
  A wrapper class/template to provide a safe handle to an underlying object.

  A safe handle is one with automatic reference counting so that
  even when multiple C++ threads are sharing the underlying object,
  the system knows when to destroy the underlying object and reclaim
  the memory.

  Original Authors (Cadence Design Systems, Inc):
  Norris Ip, Dean Shea, John Rose, Jasvinder Singh, William Paulsen,
  John Pierce, Rachida Kebichi, Ted Elkind, David Bailey
  2002-09-23

 *****************************************************************************/

/*****************************************************************************

  MODIFICATION LOG - modifiers, enter your name, affiliation, date and
  changes you are making here.

      Name, Affiliation, Date:
  Description of Modification:

 *****************************************************************************/

#ifndef INCLUDED_SCV_SHARED_PTR_H
#define INCLUDED_SCV_SHARED_PTR_H

#include <assert.h>

#ifdef SCV_USE_IOSTREAM_H
# include <iostream.h>
#else
# include <iostream>
#endif

#define LOCAL_MEMORY_MANAGEMENT \
  static int *_createCountP() { return new int(); } \
  static void _freeCountP(int *countP) { delete countP; }

template<typename T>
class scv_shared_ptr {
public:
  //
  // constructor (user-provided underlying object)
  //
  // It is the user's responsibility to make sure that no other code
  // is accessing the underlying object "core" except through safe handles.
  //
  // Typical usage:
  //   scv_shared_ptr<my_packet> packet(new my_packet());
  //
  scv_shared_ptr(T *coreP=NULL) : _coreP(coreP), _countP(NULL) {
    if (_coreP) { _countP = _createCountP(); *_countP = 1; }
  }

  scv_shared_ptr(T *coreP, int *countP) : _coreP(coreP), _countP(countP) {
    if (_countP) { ++(*_countP); }
  }

  //
  // constructor (copy)
  //
  // The new safe handle refers to the same underlying object as the
  // safe handle in the argument.
  //
  // If the argument is NULL, it is a place holder for future assignments.
  //
  scv_shared_ptr(const scv_shared_ptr<T>& t) 
    : _coreP(t._coreP), _countP(t._countP) { if (_countP) ++(*_countP); }

  //
  // destructor
  //
  ~scv_shared_ptr() {
    if (_coreP) { --(*_countP); if (*_countP == 0) { delete _coreP; _freeCountP(_countP); } }
  }

  template<typename T2>
  operator scv_shared_ptr<T2> () { return scv_shared_ptr<T2>(_coreP,_countP); }

  //
  // assignment
  //
  // The current safe handle becomes a wrapper to the underlying object 
  // of the safe handle in the argument. The reference count of the 
  // original underlying object is decrement, and the original underlying object
  // is destroyed if the reference count become zero.
  //
  scv_shared_ptr& operator=(const scv_shared_ptr& t) {
    if (t._countP != _countP) {
      if (t._coreP) ++(*t._countP);
      if (_coreP) {
  --(*_countP);
        if (*_countP == 0) { delete _coreP; _freeCountP(_countP); }
      }
      _coreP = t._coreP;
      _countP = t._countP;
    }
    return *this;
  }

  bool compare(const scv_shared_ptr& other) const {
    return this->_coreP == other._coreP;
  }

  bool isNull() const {
    return this->_coreP == NULL;
  }

  //
  // access to the underlying object
  //
  T& operator*() { 
    if (_coreP) return *_coreP;
    assert(0);
    return *(T*)0; // will cause segmentation fault when this error occurs.
  }
  const T& operator*() const {
    if (_coreP) return *_coreP;
    assert(0);
    return *(T*)0; // will cause segmentation fault when this error occurs.
  }
  T *operator->() {
    if (_coreP) return _coreP;
    assert(0);
    return NULL ;
  }
  const T *operator->() const {
    if (_coreP) return _coreP;
    assert(0);
    return NULL ;
  }
#if 0
  friend ostream& operator<<(ostream& os, const scv_shared_ptr& a) {
    os << *a._coreP << endl;
    return os;
  }
#endif

private:
  T *_coreP;
  int *_countP;

  LOCAL_MEMORY_MANAGEMENT
};

#undef LOCAL_MEMORY_MANAGEMENT

template <class T>
bool operator==(const scv_shared_ptr<T>& a, const scv_shared_ptr<T>& b) {
  return a.compare(b);
}
template <class T>
bool operator!=(const scv_shared_ptr<T>& a, const scv_shared_ptr<T>& b) {
  return !(a==b);
}
template <class T>
ostream& operator<<(ostream& os, const scv_shared_ptr<T>& a) {
    //os << *a._coreP << endl;
    os << *a << endl;
    return os;
}

#endif // INCLUDED_SCV_SHARED_PTR_H

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